As a prior art method for inspecting a wiring pattern, it is well known to provide an electrical conduction method in which probes are contacted with both ends of the wiring pattern, a cut wire of the wiring pattern is detected in response to a value of a current in the case of applying a voltage and a short circuited state of the wiring is detected in response to a presence or a non-presence of flow of current toward the probe contacted with another wiring pattern. However, a problem with such prior art method is that it was necessary to specify the position of a defect under observation with a microscope and that it took much time and labor due to the fact that the position of a defect could not be specified.
A defect inspection device manufactured by U.S. Photon Dynamics in which a planer substrate for display is processed and an electro-optical effect is utilized is described in No. 524 (Apr. 1, 1991) of the Nikkei Electronics, pp 78 to 79. This inspection device has a feature of providing a capability in which a wire cut or disconnection and a defect of a short circuited circuit are detected with an accuracy of a specifying position of a pixel unit. However, since it is necessary to float an electrical field sensing section having an electro-optical effect from a wiring pattern forming surface of the planer substrate for display by several tens .mu.m, it requires much time to make a position alignment. In addition, since the electrical field sensing section is small with respect to the planer substrate, it is necessary to repeat the sensing operation several times and its inspection time is long. Further, there is a possibility that the substrate is damaged if the electrical field sensing section contacts the wiring pattern.
U.S. Pat. No. 5,138,266 discloses a method in which a wiring pattern and a planer electrode are electrostatically coupled to each other and a presence of either a cut wire of the wiring pattern or a short-circuited state is detected. However, a planer electrode having such a size as one containing an entire wiring pattern is used and although the presence of a defect with the wiring pattern being applied as a unit can be detected, it is not possible to specify the position of the defect within the wiring pattern.
In addition, Japanese Patent Application Laid-Open No. Sho 58-388874 (1983) discloses a method for applying an AC voltage to one end of the wiring pattern, detecting an AC voltage by a probe through an inductor layer from the other end of the wiring pattern and inspecting a presence or a non-presence of a cut wire or disconnection by reference to a value of the applied voltage. However, there is no description about a method for sensing the position of the defect in the cut wire in each of the wiring patterns.
Methods for sensing a defect of each of the pixels of a TFT substrate are known in which the presence or non-presence of a defect of each of the pixels is inspected, but such methods do not disclose sensing of the position of the defect of the wiring pattern. Further, such prior art relates to the fact that electrical coupling through an electrostatic capacitance is applied and has the following problems.
Japanese Patent Application Laid-Open No. Hei 6-27494 (1994) discloses a method for varying with time a potential of each of the pixels of a TFT substrate and sensing the presence or non-presence of the defect of the pixel by applying a voltage variation detected through an electrostatic capacitance between the pixel and a probe arranged in non-contact manner on the pixel. Since it is necessary to make an accurate position setting of the probe from each of the pixel electrodes with a specified small gap, there is a problem that it takes much time for the inspection of the entire substrate. In addition, there is no description about the method for sensing the position of the defect in a cut wire of the wiring pattern.
Japanese Patent Application Laid-Open No. Hei 5-10999 (1993) discloses a method for arranging an inspection electrode at a surface of opposite side of each of the electrodes of a liquid crystal display substrate, applying a pulse voltage to each of the electrodes and inspecting a good condition or a bad condition of each of the pixels in response to a pulse detected by the inspection electrodes. This method has a problem that it is necessary to provide many probes and a selection circuit in order to select the pixels arranged in matrix, resulting in that the entire device becomes complex. Also, there is no description in the publication about a method for detecting the position of the defect of the cut wire in the wiring pattern.
Japanese Patent Application Laid-Open No. Hei 2-210391 (1990) discloses a method for inspecting characteristics of a transistor of each of pixels of a TFT substrate with reference to a frequency having a maximum displacement in phase when a frequency of an AC signal is changed by oppositely facing an inspection electrode against an arranging direction of the pixels in one row of the TFT substrate, applying an AC signal and detecting a displacement in phase between the applied AC signal and an AC signal to be detected. Also in this publication, it is assumed that no defect is present at the wiring pattern and a method for detecting the position of the defect in the wiring pattern is not indicated.
Further, a method of repairing disconnections of a wiring pattern on a substrate of an integrated circuit and display device is described in the Japanese Patent Application Laid-Open No. Hei 2-19838 (1990). This prior art describes that a disconnection fault point of a wiring pattern formed on a glass substrate is coated with a composition which can precipitates a conductive substance only at a relatively high temperature (a nitrate of metal, for example, manganese nitrate and moreover an organic metal compound such as ruthenium, etc.) and the periphery of such disconnection fault is irradiated with a laser beam to precipitate a conductive substance (a low resistance manganese dioxide, low resistance ruthenium oxide) in view of repairing a wiring pattern.
As another known prior art, a method of repairing a white point fault of a photomask is described in Japanese Patent Application Laid-Open No. Sho 59-177358 (1984). This prior art describes that liquid drops of an organic metal solution including Cr, Mo metals are deposited on a white fault point of a photomask under an inactive gas atmosphere and the deposited point is irradiated with a laser beam to correct the white fault by depositing metal thin films of Cr and Mo.
Additionally, a method of repairing a disconnected Cu circuit pattern of a printed circuit board is described in Japanese Patent Application Laid-Open No. Hei 2-101188 (1990). This prior art describes that an end part of disconnected Cu circuit pattern of the printed circuit board is cut obliquely with a knife with respect to the substrate to form a taper, a plating solution is supplied to a plating part including this end part and this plating part is plated by irradiating the plating solution with a laser beam.
In an electronic circuit substrate represented by a liquid crystal display or a semiconductor integrated circuit, the circuit wiring formed on the substrate is being made finer and given higher density with improved display performance and integration. Such circuit wiring is normally formed by a series of processes such as resist coating, exposure, development, etching, and resist peeling, but as the tendency of the electronic circuit substrate toward higher performance advances, the yield of good products in the above processes lowers. Particularly, a disconnection defect of wiring resulting from foreign particles during resist exposure is fatal, and it is regarded as a defective product in many cases even if a disconnection defect takes places only at one place on the substrate. Accordingly, in order to improve the yield of manufacture, that is, to reduce the product cost, the technique of correcting an absence of such as a disconnection or cut wire or a defective wiring pattern is indispensable.
As a conventional technique for forming wiring on a substrate, a method of Japanese Patent Application Laid-Open No. Hei 6-104255 (1994) has been disclosed. More specifically, this method provide for scanning a stage carrying a substrate while supplying conductive material paste at any position on the substrate using a dispenser, and to irradiate a laser light in synchronism with its supply for heating the conductive material paste in order to continuously form a metal film. In this case, it is sufficient to supply the conductive material paste to only a portion where a metal film is to be formed, and since the metal film is obtained by irradiating a laser light onto all the supplied conductive material paste, it is not necessary to remove paste adhered to unnecessary portions.
Also, in Japanese Patent Application Laid-Open No. Hei 4-277692 (1992), there is disclosed a method to form a groove pattern on a ground film in a disconnected portion by means of a laser light, to supply organic metal solution into the groove for setting by heating, and further to irradiate a laser light for making it into a conductive material in order to connect the disconnected portions. This method makes it possible to prevent the material from adhering to the unnecessary portion by controlling the amount of supplied organic metal solution, and improves the reliability for the joints because the connected area between the wiring disconnected end portion and the formed metal is increased.
As described above, the prior art methods for inspecting a wiring pattern had some problems in that the position of a defect in the wiring pattern could not be specified and it took much time for performing the inspection for entire substrate.
Additionally, since a circuit wiring provided on a circuit substrate represented by a liquid crystal display device and a semiconductor integrated circuit element is usually produced by a series of processes including coating of photoresist-exposure-development-etching-separation of resist, disconnection failure of wiring has been generated due to existence of foreign materials generated during this process. Meanwhile, such circuit wiring has been ultra-miniaturized in accordance with improvement of display performance and integration density. Applicants have determined that the prior art described above is deficient in not sufficiently referring to the problem of connecting a disconnected point of a fine wiring with almost the same function as the circuit, a similar resistance value and with higher reliability considering the possibility of application as an actual product.
The prior art concerning the formation of wiring on the substrate has the following problems because the conductive material paste is supplied in synchronism with the irradiation of laser light.
The liquid material, in which the material is crystallized or decomposed/precipitated by heating to obtain a metal film, has generally great volume shrinkage after heating, and therefore, when the disconnected width is almost larger than the wiring width or than the laser irradiation size for heating the liquid material, a step-cut of the formed metal occurs near the disconnected end portion. The phenomenon will be described with reference to FIGS. 28(a)-28(j), which show plan views and corresponding cross-sectional views. When a wiring is disconnected as represented by end points 522 and 522' on the surface of a substrate 521 in FIGS. 28(a)-28(d), a dispenser (not shown) supplies liquid material 523 to the disconnected portion while scanning a stage (not shown) as shown in FIGS. 28(e)-28(h). Subsequently, the supplied liquid material 523 reaches an irradiation region 524' for laser light 524 by a scanning of the stage (not shown). When the laser light is irradiated onto metal wiring of Al, Cu or the like, which is normally often used as wiring material for a circuit substrate, the greater part of the laser light is only reflected, but a part thereof is absorbed to enable the wiring to be heated. In this respect, these wiring materials have generally high thermal conductivity, and therefore, the temperature at the disconnected end point 522 is raised due to the conductive heat caused by the irradiation of the laser light 524.
As shown in FIGS. 28(e)-28(i), the liquid material 523 supplied near the disconnected end portion 522 is sufficiently heated for decomposition, thus satisfactorily achieving the connection between the end portion 522 and the precipitated metal film 523'. Since, however, exceedingly great volume shrinkage occurs when the supplied liquid material 523 is heated to become a metal film, an influx 525 of the liquid material 523 before the heating occurs on the precipitated metal film 523', but does not affect the connecting capability at the disconnected end portion 522.
In this way, in the vicinity of the laser irradiation region 524', the treatment always goes on accompanied by an influx 525 of the liquid material 523 on the precipitated metal film 523'. The laser light 524 moves relative to the substrate 521, and successively heats the liquid material 523 on the substrate 521 to thereby form a metal film 523', reaching near the disconnected end point 522' as shown in FIGS. 28(g)-28(h). However, in the vicinity of the disconnected end point 522', an influx 525 of the liquid material 523 on the end point 522' occurs to thereby reduce the volume of the liquid material 523 on the end point 522'. This further reduces the thickness of a metal film 23' precipitated in the vicinity of the end point 522' as shown in FIGS. 28(i)-28(j) to cause a step-cut 526 of the metal film 523'. In other words, influenced by the thickness distribution of the metal film after the precipitation, the disconnected portions are not electrically connected, or the connection is made with a high electric resistance, resulting in failure to correct the disconnection defect. Further, at the initial stage when the laser light 524 is irradiated onto the disconnected end point 522', heat dissipates from the end point so that the temperature of the end point is not increased, and this leads to a problem that heating of the liquid material on such end point is insufficient.
On the other hand, in the prior art in which a groove pattern is formed in a ground film of the disconnected portion, and the liquid material is supplied into the groove to connect the disconnected portions, an ultraviolet laser light for forming the groove pattern is newly required, resulting in a larger apparatus and higher product cost. Also, it takes longer time to correct the defect.